Chelated potassium and arginine supplementation in diets of Pacific white shrimp reared in low-salinity waters of west Alabama

Dietary supplements have been proposed as a potential remediation strategy to counteract mineral deficiencies in low-salinity well waters (LSWW) used for shrimp, culture in Alabama. Existing strategies (i.e., application of fertilizers such as K-mag and muriate of potash) are costly to farmers attempting to raise levels of potassium (K+) in their ponds. Previous laboratory studies using dietary supplements of chelated K+ increased growth but not survival of Pacific white shrimp Litopenaeus vannamei reared in low-salinity water. To determine whether this approach is applicable in the field, two growth trials were conducted in flow-through outdoor tanks that used water from farm ponds. The first trial (6 weeks) was conducted simultaneously at two separate low-salinity farms in west Alabama and evaluated two practical diets, one with a chelated K+ supplement and one without. One of these farms supplements K+ to its water and is considered a low-stress environment (LSE), while the other farm does not supplement its water and is considered a high-stress environment (HSE). Results indicated that dietary supplementation of K+ (1.0%) in the absence of an appropriate ionic profile (i.e., the HSE) failed to enhance growth or survival of Pacific white shrimp. Another 9-week growth trial was conducted at the LSE farm. Shrimp were offered either a practical basal diet or the basal diet supplemented with 0.5% chelated K+, 1.0% chelated K+, or 0.4% arginine. Although no statistically significant effects of chelated K+ supplementation were observed, results of this experiment and two other experiments showed an increase in growth associated with chelated K+ supplementation, indicating a marginal benefit. Present results do not justify K+ supplementation of diets for Pacific white shrimp reared in inland LSWW. Better shrimp survival and growth are observed when K+ is added to culture waters to mitigate imbalances in Na:K and Cl:K ratios.